1. Field of the Invention
The present invention relates to an autonomous control system for a vehicle and the method thereof and more particularly to an autonomous control system and the method of an unmanned vehicle which can be operated by identifying a position selectively by a magnetic guidance system or by an autonomous guidance system.
2. Prior Arts
When an off-road vehicle runs autonomously and conducts field work such as mowing lawn or grasses in golf courses, it is important to be able to correctly identify the position where the vehicle is presently located.
There has been a magnetic guidance system in which the vehicle is operated by sensing a magnetic field generated from a magnetic rail laid underground. Further, as examples of recently proposed techniques, Japanese patent application laid open No. Toku-Kai-Sho 63-247612 discloses a technique for finding a vehicular position by receiving a radio wave transmitted from a satellite and further No. Toku-Kai-Hei 2-132321 discloses a technique using a dead reckoning navigation method by which the location of a vehicle is estimated from a running distance and a running direction.
The first technique by the magnetic guidance system is a technique needed when a vehicle is operated at the location where an accurate positioning is required, such as in an area having a lot of obstacles or ups-and-downs, however, this technique has a disadvantage that it costs much money to lay the magnetic rails underground covering a broad golf course or park.
Further, the second technique using a satellite lacks accuracy when it is applied to an autonomous controlled vehicle which travels within a relatively narrow range, because of a clock error of the satellite and the receiver, an orbit error of the satellite, delays of radio wave caused by an ionized layer, a delay of radio waves affected by the atmosphere, and a multipass.
Further, in the third technique using a dead reckoning navigation method, there is a disadvantage that errors are accumulated with an increase of the distance travelled.